@tnguyen449 you are right. in 2017.1 we have added a reference field which is going to be “queryable” and can be used to enforce the unicity of an item in 2017.1 SP1 (one month)
ashokkarale
MD_Farhan1
Ajay_Mishra
postwick
Dheerendra_vishwakarma
Anil_G
chandreshsinh.jadeja
Gautham_Pattabiraman
vrdabberu
aravindbalineni123